The RG+WD symbiotic stars are broadly divided into two major groups (see the
recent review by [1]} for details): those accreting-only (acc-SySt) whose optical spectra are dominated by the
RG with no or weak emission lines, and the burning-type (burn-SySt) displaying a strong nebular continuum and a rich emission line
spectrum: they originate from the wind of the RG, which is largely ionized
by the very hot and luminous WD undergoing surface nuclear burning of
accreted material.
